Recently, in a recording reproducing apparatus using a tape medium, there is a growing demand for a recording apparatus which is long time-recordable and accomplishes a quick access. Regarding the high access, the increase of a tape transport speed and the reduction of acceleration and deceleration times are the technical problems to be solved.
Tape transport apparatuses are disclosed in, for example, Japanese Laid-Open Patent Publication No. 59-165260 and Japanese Laid-Open Patent Publication No. 59-165261.
An example of a conventional tape transport apparatus is described below.
A conventional tape transport apparatus comprises a winding reel, a supply reel, two rotation-number detectors for detecting the number of rotations of the two reels, two rectification smoothing devices for smoothing the outputs of the rotation-number detectors, an adder for adding the outputs of the two rectification smoothing devices, a comparator for comparing the output of a speed setting signal indicative of a tape speed with the output of the adder, an integrator, and a reel motor.
Regarding its operation, the rotation condition of the winding reel is detected by the first rotation-number detector and transmitted to the adder through the first rectification smoothing device. Similarly, the rotation condition of the supply reel is detected by the second rotation-number detector, transmitted to the adder through the second rectification smoothing device, and added to the output of the first rectification smoothing device. The comparator compares the speed setting signal with the output of the adder and the result is outputted to the integrator as a speed error signal. In order for the reel motor for driving the winding reel to receive the integrated speed error signal, the rotation of the winding reel is feedback-controlled.
However, according to the above-described construction, it is difficult, in particular, to control the torque applied to the winding reel when the tape speed is reduced. Desirably, a deceleration torque is applied to the winding reel in order to reduce the tape speed, but the tape is loosened if the deceleration torque is too large.
If the reduction torque is applied to the supply reel, the operation is a special processing to temporarily release the feedback control over the winding reel in the transient condition in which a high speed transport is switched to a low speed transport. Thus, the known tape transport apparatus has a problem that it has difficulty in controlling in detail, for example, the deceleration torque amount and deceleration time.